Such a washing apparatus conventionally comprises a jet nozzle which is supplied with washing liquid under pressure and which is fixed in a position spaced in front of, and below, the headlamp glass. Thus such a jet nozzle is commonly incorporated in the front fender or cross beam of the vehicle.
It is also well known that, in order to obtain maximum washing efficiency, the jet nozzle must be arranged as far as possible in front of the headlamp glass, in such a way that the droplets of liquid will impinge on the glass at an angle of incidence which is as large as possible.
In addition, the glasses of modern headlamps, which may follow the "diving" front profile of the vehicle, make it necessary to locate the jet nozzles further and further in front of the headlamp glass. Since such jet nozzles are conventionally incorporated in upward projections carried by the fenders, this gives rise to drawbacks in connection with safety, aerodynamics and aesthetics.
It has previously been proposed, in order to overcome these drawbacks, to provide a retractable jet carrier carrying the jet nozzle and being of a type that comprises a jack, the internal movable piston of which carries the nozzle at its free end. The chamber of the jack is supplied directly with the washing liquid, and the pressure of the latter first causes the jack to operate so as to move the jet nozzle into a position in which it projects forward, by displacement of the piston, after which it causes the nozzle to be supplied with the liquid so as to spray the glass itself. Such arrangements are described in the specifications of the French published patent application No. FR 2 523 909A and European published patent application No. Ep 0 262 402A.
However, these known types of jet carriers have a certain number of drawbacks themselves. By virtue of their particular construction, the sealing zone between the two movable members constituting the cylinder and piston of the jack is exposed to the front of the vehicle, so that there is a major risk of deterioration which leads to leakage of washing liquid, or even to jamming of the piston. The apparatus described in the above mentioned European patent document includes, besides a seal between the cylinder and piston of the jack, a protective bellows which completely surrounds the jack piston in that part of the latter which is outside the cylinder. The selling cost is thus increased, and such a bellows is considered unattractive aesthetically.
Besides the foregoing, these two known apparatuses necessitate complicated means for ensuring the initial extension of the jack without the jet nozzle being supplied with liquid under pressure until the jack is extended to the required position.